1. Field of the Invention
The present invention relates to a process for the manufacture of organic polymer polyol dispersions having a water content of 0.2 to 5 percent by weight by dehydration of the reaction products of polyhydroxyl compounds and aqueous polymer dispersions.
2. Description of the Prior Art
By mixing organic polyhydroxyl compounds with aqueous polymer dispersions having solids contents of 20 to 65% by weight relative to the total weight in weight ratios of 1 to 0.05 to 1 to 2, aqueous polymer polyol dispersions having viscosities of 5 to 5,000 Pas are formed. Due to the resulting great viscosity, the complete mixing of the raw materials is either not possible, or possible only after long, intensive stirring requiring considerable energy. Also because of decreased viscosity of the mixture, the water only slowly diffuses to the liquid surface in order to evaporate. In the case of non-homogeneous mixtures, the separation of the water results in a coagulation of the batch. Coagulation also is frequently incurred with large batches in commonly used mixing vessels due to the prolonged temperature stress.